Catheters for the drainage of body cavities, such as the bladder or the peritoneal cavity or the thoracic cavity, are known to the art. One example of such a catheter is provided as a set with a stiffening cannula which is inserted into an axial lumen extending to the distal tip region and has, as an additional second element, an elongated trocar stylet which is inserted through the stiffening cannula with its sharpened tip projecting through the distal tip of the catheter. The sharpened stylet tip is pushed through the skin and the cavity wall. Thereafter, the stylet is removed and a wire guide may be inserted through the stiffening cannula and the catheter advanced off of the cannula until it is properly placed within the cavity. The stiffening cannula and the wire guide are then removed, and the catheter is connected to the appropriate drainage system. Although the product described above is satisfactory for many applications, the size of catheter employed is relatively small in diameter since, in larger sizes, the pressure which must be applied to the proximal end of the catheter in inserting it into the cavity tends to cause the catheter material to bunch up on the stiffening cannula with the result that insertion becomes quite difficult and traumatic, particularly when catheters made of a very soft and pliable material are employed.
The prior art also includes U.S. Pat. No. 4,636,199 which discloses apparatus for inserting a catheter into the intercostal space of a human body for the removal of unwanted fluid, such as air or blood. According to the '199 Patent, a syringe having a hollow needle is first inserted into the intercostal space. After verification that the distal tip of the needle is within the space, the syringe is detached from the needle and a wire guide inserted through the needle lumen. The needle is then withdrawn over the wire guide and a catheter having an elongated trocar projected from its distal tip is threaded over the wire guide. The trocar has a flared proximal end portion which interfaces with a similar flared portion of the catheter. As the trocar is pushed into the cavity, the force is transmitted to the catheter and the two are moved as a unit into the intercostal space. The wire guide and the trocar are then removed, and the catheter is attached to the conventional suction or drainage equipment. Like the drainage set first described, the catheter material has a tendency to bunch up as the catheter is inserted, making insertion more difficult and more traumatic to the patient.
U.S. Pat. No. 2,828,744 to Hirsch et al discloses a vascular catheter in which a shoulder on a needle cooperates with a mating surface formed by the end of a sleeve so that the needle fits within what is termed an "external needle". The internal needle imparts stiffness to the end portion of the external needle to facilitate insertion into a blood vessel.